javascript html页面中的内容替换

<script language="javascript">

function ffRed(){

 var xsxf = document.getElementById("id");

 var str2 = "字段1";

 var str3 = "字段2";

 var reg=eval("/"+str2+"/gi");

 var reg3=eval("/"+str3+"/gi");

 xsxf.innerHTML =  xsxf.innerHTML.replace(reg,"<font color='#FF0000'>字段1</font>");

 xsxf.innerHTML =  xsxf.innerHTML.replace(reg3,"<font color='#FF0000'>字段2</font>");

}

ffRed();

</script>